It makes sense to research the cost of living when planning a move abroad -
but with so many statistics floating around, crunching the numbers can prove
tricky.

Is Tokyo, Oslo or Luanda the most expensive city for an expat to live in?

The answer is that it depends on which survey you read. With so much research available on the cost of living for expats, it can be hard to work out which city really is the priciest.

Mercer, ECA and the Economic Intelligence Unit(EIU) provide the most comprehensive surveys in this field. While Mercer produces an annual survey, the other two provide twice-yearly ones adding to the confusion.

The reason why they differ over which is the most expensive city is that each organisation uses a different set of criteria - and not all three cover the same cities.

Mercer's Cost of Living survey ranks 214 cities and compares more than 200 items in each city. These include housing, transportation, food, clothing, household goods and entertainment.

It produces a paid-for report which can help multinational companies and governments set compensation for their expat employees. This year it ranked the Angolan capital Luanda as the world’s costliest city for expats.

Two main factors determine a city’s ranking, according to Mercer. These are the relative strength of the relevant currency against the US dollar and price movements over the prior 12 months compared with those in New York.

The Economist Intelligence Unit's Worldwide Cost of Living ranking does not include the price of housing, which is typically the largest proportion of an expat’s living expenses. Instead, it compares more than 400 individual prices across 160 products and services. These include food, clothing, transport, utility bills, private schools, domestic help and recreational costs.

The survey itself is designed to calculate cost-of-living allowances and compensation packages for expats and business travellers. Having surveyed 140 cities, the first survey this year found Tokyo to be the most expensive.

ECA International calculates the cost of living for expats in almost 400 cities. The survey doesn’t include living costs such as accommodation, utilities and school fees.

These are significant expenses, but ECA argues these are usually compensated for separately in expat packages.

Instead, the survey covers a wide variety of consumer goods such as groceries, drinks, tobacco, clothing and eating out. ECA’s recent survey found Oslo to be the most expensive city for an expat to relocate to.